Academic Discussion on the History and Theory of the Historical Sciences

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<7:80>From SMD@utkvx.utk.edu Mon Mar 21 22:03:22 1994
Date: Mon, 21 Mar 1994 23:03:16 -0500 (EST)
From: "Steven M. Donnelly" <SMD@utkvx.utk.edu>
Subject: evolving rodents
To: darwin-l@ukanaix.cc.ukans.edu
As requested by popular demand the references regarding widespread phyletic
evolution in rodents are:
Chaline J and Laurin B (1986) Phyletic gradualism in a European
Plio-Pleistocene Mimomys lineage (Arvicolidae, Rodentia). Paleobiology
12:203-216.
Freudenthal M (1965) Betrachtungen uber die Gattung Cricetodon.
Koninklijke Akad Wetenschappen (B) 68:293-305.
Martin RA (1970) Line and grade in the extinct medius species group of
Sigmodon. Science 167:1504-1506.
Several years ago I made a cursory search of the literature looking for
examples of 'phyletic gradualism' or stasis in fossil lineages and was able
to find, without too much trouble, quite a few examples of 'gradualism'.
Most of these though, were from fossil samples taken from a limited
geographic area, e.g. forams from a single bore-hole, or bore-holes that
were near each other, Eocene primates from Wyoming, brachiopods from a single
formation.
The small number of examples of widespread phyletic evolution must be due
in part to the spotty fossil record. Eocene primates didn't live only in
Wyoming, but their fossils happen to be abundant there today. If I wanted to
study evolutionary trends in Australopithecus afarensis I'd be limited to
fossils from one restricted geographic area--Ethiopia and Tanzania--because
that's where the fossils come from. Who knows how widespread A. afarensis
might really have been. And if I show that, for example, the molars
increase significantly in size through time within the species as it's
represented by the fossils, I have no way of knowing what happened in other
areas in other populations.
Steven Donnelly
Department of Anthropology
University of Tennessee-Knoxville
BITNET: smd@utkvx
INTERNET: smd@utkvx.utk.edu